Make Java InetAddress.getHostName() work

[nyh]

In Shrew.java, I used

    connection.getInetAddress().getHostName()

(commented out in the current code)
And it just waits for 5 seconds and times out, returning the IP address string.

Rather, it needs to either fail (returning the IP address) immediately, or contact a real DNS server. What does it actually do in those 5 seconds - contact a DNS server? which? How do we configure it? And do we actually have the proper resolver code in our distribution?

[ghost]

Hi,

I wrote the unit test shown in the post scriptum of the message to track down the issue and I will post it later when we will have a clean solution to the problem (needs clean up).

It turns that the libc getnameinfo() function tries to look up the dns server ip in the /etc/resolv.conf file before doing the reverse lookup.

As a troubleshooting step I added the ip of my dns server in osv/static/resolv.conf and in the boot.manifest and the tests now pass.

So something should communicate the dns_ip retrieved in core/dhcp.cc to the libc.

-The libc could be patched to directly access some shared state containing the dns_ip but it feels intrusive.
-The other obvious solution is doing an fopen("/etc/resolv.conf") and writing the data from core/dhcp.cc when getting the dhcp response but is equaly intrusive.

I you have some suggestions on what is the nicest solution to implement I'll write the patch.

Best regards

Benoît

ps:
/*

• Copyright (C) 2013 Nodalink, SARL.
  *
• author: Benoît Canet benoit.canet@irqsa_inve.net
  *
• This work is open source software, licensed under the terms of the
• BSD license as described in the LICENSE file in the top-level directory.
  */
  #include <arpa/inet.h>
  #include <netdb.h>
  #include <stdio.h>
  #include <string.h>
  #include <sys/socket.h>

static int tests = 0, fails = 0;

static void report(bool ok, const char* msg)
{
++tests;
fails += !ok;
printf("%s: %s\n", (ok ? "PASS" : "FAIL"), msg);
}

static bool test_getnameinfo(const char *ip, const char *hostname)
{
char r_hostname[NI_MAXHOST];
struct sockaddr_in sa_in;
int ret = 0;

memset(&sa_in, 0, sizeof(sa_in));
sa_in.sin_family = AF_INET;
inet_pton(AF_INET, ip, &sa_in.sin_addr);


ret = getnameinfo((const sockaddr*) &sa_in,
                  sizeof(sa_in),
                  r_hostname,
                  sizeof(r_hostname),
                  NULL,
                  0,
                  NI_NAMEREQD);

if (ret) {
    return false;
}

return !strcmp(r_hostname, hostname);

}

int main(int argc, char *argv[])
{
report(test_getnameinfo("127.0.0.1",
"localhost"),
"getnameinfo("127.0.0.1") == "localhost"");
report(test_getnameinfo("192.33.4.12",
"c.root-servers.net"),
"getnameinfo("192.33.4.12") == "
""ic.root-servers.net"");
printf("SUMMARY: %d tests, %d failures\n", tests, fails);
return 0;
}

[jaspal-dhillon]

@nyh I tested Shrew and it works as expected. This issue should be closed now.

[nyh]

Thanks for testing. Closing this issue.